1. Field of the Invention
This invention is related to the field of digital systems including integrated circuits, display devices, and caches.
2. Description of the Related Art
Digital systems of various types often include, or are connected to, a display for the user to interact with the device. The display can be incorporated into the device. Examples of incorporated displays include the touchscreen on various smart phones, tablet computers, or other personal digital assistants. Another example of the incorporated display is a laptop with the screen in the lid. The display can also be connected to the device via a cable. Examples of the connected display include various desktop computers and workstations having a separate display that resides on the desk in front of the user. Some desktops also have an incorporated display (e.g. various iMac® computers from Apple Inc.). The display provides a visual interface that the user can view to interact with the system and applications executing on the system. In some cases (e.g. touchscreens), the display also provides a user interface to input to the system. Other user input devices (e.g. keyboards, mice or other pointing devices, etc.) can also be included.
In many cases, the images being display over a period of time are essentially static. For example, if the user is reading an ebook on the display, the display may be statically displaying a page of text until the user is finished reading the page. When a movie is paused, there may be no change in the images for the time that the pause is in effect. When a user is browsing web pages, again the user may be absorbing content and the images may be static. When there is little or no change in the static images being displayed, the memory bandwidth consumed to fetch the image each refresh cycle of the screen may be wasteful in both the bandwidth and in power consumed.